In recent years, means for rapidly transmitting terabyte-class information have developed remarkably, making it possible to transfer images and data providing immense information. With the development, demands for high technology for recording, reproducing, and storing the information have been increasing. Types of media for recording and reproducing information include flexible discs, magnetic drums, hard discs, and magnetic tapes. In particular, magnetic tapes have a high storage capacity per pack and are expected to meet the demands in applications to data backup and the like.
According as the use of magnetic tape spreads, magnetic tape has been required to have higher reliability for use, such as data storage, in broader use environments (especially under largely varying temperature and humidity conditions) as well as higher reliability on performance, such as stable data writing and reading, in repeated high speed running than before.
Conventional digital recording magnetic tape formats for computer use are standardized according to the read/write systems. For example, D8, DLT, and DDS formats are known. These magnetic tapes each include a nonmagnetic support, a magnetic layer containing a ferromagnetic powder and a binder on one side of the support, and a backcoat layer for securing winding quality and good running durability on the other side.
Magnetic recording media having a dual layer structure to minimize reduction in read output due to the thickness loss are known, in which a lower nonmagnetic layer having an inorganic powder dispersed in a binder is provided on a nonmagnetic support, and an upper thin magnetic layer with a thickness of 1.0 μm or less having a ferromagnetic powder dispersed in a binder is provided on the nonmagnetic layer while the nonmagnetic layer is wet.
Magnetic tapes are generally produced by processes including the steps of preparing a coating composition for each of constituent layers, applying each magnetic coating composition to a web of a nonmagnetic support, subjecting the coated web to drying, calendering (surface smoothing), and slitting to width, and winding the resulting tapes into individual cartridges. In the steps of coating composition application, drying, and calendering, the web (the coated or uncoated support of continuous form) tends to be stretched because it is handled or processed under a certain tension (for example, of about 10 kg/m in the steps of application and drying) while being unrolled from a roll of the web. After the tape cartridge production, the tape pack in the cartridge gradually contracts radially with time to cause deformation of the tape.
In order to overcome the problem, JP 10-69628A and JP 10-134337A propose using an aromatic polyamide as a nonmagnetic support. An aromatic polyamide film has higher strength than PET or PEN films and therefore may be made thinner to provide a tape with a longer length and an increased recording area per pack. It has been used as a support of compact data storage formats, such as DDS and DAT72.